David A. Stockman's big black book of budget cuts, 145 pages of numbers and fine print, makes tangible what official Washington was already beginning to grasp: the Reagan crusade for federal reform is not business-as-usual. It promises, instead, to produce a year of epic political struggle unlike anything seen before in modern Washington.

When President Reagan presents his detailed economic proposals 10 days from now, the struggle will begin in earnest. In the meantime, the budget-cutting prospectus prepared by budget director Stockman and obtained yesterday by The Washington Post will be the best-read official document in the capital, widely circulated and scrutinized in Congress and in lobbyists' offices.

The sum of its details is breath-taking: enormous reductions proposed for long-familiar and popular federal programs. Stockman proposes to cut scores of billions: in some cases he would cut the benefits that significant elements of the population depend on for their survival.

In the first days of his presidency Reagan has apparently settled easily into the idea of fighting this radical crusade, which in fact is closer to the apocalyptic rhetoric of his early political career than the soothing reassurances of last year's presidential campaign. Candidate Reagan often seemed to be saying that the only thing that had to be cut was federal taxes in order to restore the country's economic well-being. Now President Reagan predicts "an economic calamity of tremendous proportions" unless radical surgery is performed on the federal budget.

The difference between the campaign rhetoric and the new budget-cutting crusade is one of the political problems that the administration will have to conquer to prevail. "The candidate in 1980 who asked for sacrifice," recalled Rep. James R. Jones (D-Okla.), chairman of the House Budget Committee, "lost the election." But now the man who won will be asking for literally unprecedented sacrifices from individual Americans and some formidable interest groups.

Many in the White House, including Stockman, who is the principal architect of the budget-cutting plan, believe speed and momentum are crucial to their success. The idea is a political blitzkrieg backed by a persuasive president's direct appeals to the nation for support. Reagan's televised address Thursday night was the first diplay of these tactics.

But the budget process takes Congress most of the year to complete, and it is beyond the power of the White House to accelerate that schedule. Reagan can win some quick skirmishes, for example in his effort to reduce the current budget by about $14 billion, but the truly revolutionary cuts he seeks in fiscal year 1982 and beyond won't be voted on until much later.

This unavoidable delay will give the special-interest groups -- from welfare mothers to dairy farmers to Exxon and Boeing -- ample time to mobilize their political forces to try to frustrate the administration's proposed cuts. "There are probably 35 meetings along the K Street corridor right now, trying to plan how to stop this," one White House official said with evident relish for the battles ahead.

The outcome of this contest remains unpredictable, not least because unforeseeable events can easily prove decisive.For example, the White House is hoping to keep national attention focused on the budget issue until it is resolved, but an international crisis -- a Soviet invasion of Poland, say -- could distract both the country and the White House, opening up new maneuvering room to the interest groups.

But there is widespread agreement on this point: Reagan seems to have an opportunity for success which his predecessors lacked, a sense of political readiness and nervousness that simply was not present in previous seasons of much-heralded budget cutting. Two dozen interviews with White House officials, members of both houses of Congress and professional lobbyists suggest both why Reagan could win his crusade, and what might tear it apart.

Administration officials and their allies in Congress suggested these elements are necessary ingredients in a winning strategy:

A demonstrably fair plan for budget cuts, in which all special interests are seen to share in the sacrifices. This has been Stockman's objective all along, though some Republican members of Congress fault him for leaning too heavily on poor people in his initial planning. Stockman even hopes to surprise Congress by proposing some cuts in the Pentagon's budget, though these will be more than matched by new increases.

The theory of a balanced package of cuts was summed up neatly by Tom Korologos, a prominent Washington lobbyist who is close to the White House.

"If the Business Roundtable isn't furious when this is over," Korologos said, referring to the group that represents the sentiment of America's biggest corporations, "it will have failed. Everybody has got to scream equally -- a loud outcry. Then it might fly."

Of course, fairness of this kind is much easier to describe than to achieve. Some of the oxen that will be gored by Reagan's budget cuts will never believe that they are suffering "fairly," and will fight back accordingly.

One key White House official who asked that his name not be used said at the end of the week that after the first leaks of the Reagan cuts he was "really surprised at the reaction on the Hill." People he expected to be fierecely opposed to the cuts are accepting them with unexpected equanimity, this official said.

Preservation of the post-election political mood in Washington, which is clearly favorable to Reagan's cause. Politicians from liberal Democrats to arch-conservative Republicans agree that November's surprising results -- both Reagan's large margin of victory, and the Republicans' unexpected gains in Congress -- have intimidated even the House Democrats who remain in control of that body.

Rep. Thomas S. Foley (D-Wash.), the new majority whip in the House said last week that "there's a consensus growing in the Congress" in favor of less government spending, fewer government regulations and simplified government programs. "The inflation level is the most serious issue facing the country," Foley said.

If even liberal Democrats are talking like that, Reagan clearly has an advantage. "I think the climate is somewhat intimidating," said Rep. Barber Conable (N.Y.), the ranking Republican on the Ways and Means Committee. "Of course, the conventional wisdom is that this climate won't last long."

The evolution of shifting coalitions of budget-cutting members of both houses to head off the pet projects of key members. Sen. Jesse Helms (R-N.C.) is a convinced budget cutter, but he doesn't want to touch the tobacco subsidies so important in his home state. If he can protect them -- or if the dairy industry's many friends in Congress can protect dairy subsidies, or if the western senators and representatives preserve all the expensive water projects -- the spell of unity Reagan hopes to cast will be broken. Other interests will pursue their pet projects with renewed indignation. The Stockman plan will be plucked and pulled from every direction at once. White House officials say they are keenly aware of this problem.

Top-flight lobbying work all year. After last week's vote to raise the debt ceiling in the House, when three-fourths of the Republicans were persuaded by the White House to support a measure they had all but unanimously opposed in the past, Rep. Richard Bolling (D-Mo.), chairman of the Rules Committee, observed: "The day of the amateur [president] is passed . . . These guys are really going to be playing legitimate, effective hard ball."

These same people see many different ways that the new president's crusade could be frustrated, too. Among them:

A loss of nerve among Republicans who can't stomach cuts of the programs that many of their constituents depend on. Sen. Bob Dole (R-Kan.) said last week that he has repeatedly reminded the White House that six of the Republicans on the Finance Committee he now chairs will be up for reelection in 1982, and thus will have to answer for whatever the Republican-controlled Senate has done in the interim.

If a united front is broken, several Republicans in both houses said, the whole plan could quickly unravel.

A changed atmosphere on Capitol Hill. A serious economic downturn, for example, could revive traditional congressional instincts and promote new round of pump-priming through the federal budget. "You've got 100 senators each holding one finger up in the air to see which way the wind is blowing," said an aide to a prominent Senate liberal, who admitted that today's wind is favorable to budget cuts.

An outbreak of regional warfare in Congress. Many of today's big government programs -- all of which Reagan will try to trim -- were the product of elaborate regional compromises. For example, food stamps and price supports and subsidies for farmers have traditionally been seen as a trade-off between rural and urban members of the House. Northern members made trades to win Sun Belt support for the fuel-aid program to help poor people pay for their heating oil or gas. Western members traded votes on matters of interest to northern and eastern colleagues to win support for their water projects.

If the budget-cutting process destroys any of these explicit and implicit arrangement, "there's a real danger of sectionalism dividing the Congress," said Sen. Patrick J. Leahy (D-Vt.).

Squabbling between members whose first interest is tax cuts and those who are more anxious about spending cuts.

So far, Stockman has held the two camps together by allying the new administration with both of them. But there are members of both parties who would be perfectly willing to vote tax cuts before spending cuts are agreed on, and others who will fight such a move bitterly.

In the end Reagan's most formidable foe may be the traditions of politics as usual that have governed Capitol Hill for so long. The new president wants a revolution in bread-and-butter politics, but many in Congress can be expected of offer him half a loaf.